cooler test
Updated Sept 24, 2001
Flow is not the end-all be-all test for intercoolers, but it is VERY important! If your turbo has to make 5 extra psi to hold your desired boost level, you are overheating the air by about 55 degrees, which means your "high efficiency" cooler may become "low efficiency" in short order. These flow results DO NOT show the cfm flowed; they show how the coolers were tested for flow IN RELATIONSHIP TO EACH OTHER.
This relationship is *NOT* LINEAR!
I should mention that COMPLETE blockage of the leaf blower outlet produces only 13" H2O above the straight pipe.
This means that an increase of one inch H2O from 10" to 11" represents a MUCH LARGER gain of backpressure than an increase of one inch H2O from 4" to 5".
Nevertheless, this test tells which cooler outflows which, and allows you to go from there in your selection.
Here are the results of the test, starting with the best flowing cooler, and descending to the worst flowing:
1. SPEARCO intercooler. 32
short thick wide tubes. 4" H2O
2. TALON intercooler. 42 short
thin narrow tubes. 6" H2O
3. FORD intercooler.
17 short thick wide tubes. 8.5"
H2O
4. VOLVO intercooler. 34 long
thin narrow tubes. 9" H2O
5. MOPAR intercooler. 10
long thick wide tubes. 9.25" H2O
6. SAAB intercooler. 26
long thin narrow tubes. 10"
H2O
Here's how the results were derived:
As you can see, the abrupt change from over 3" ID to a 2.5" pipe hampers
flow. So we get 2" of backpressure from a simple short straight 2.5" pipe.
Therefore backpressure of the coolers is measured in inches of water *above*
2".
This would give the large-inlet Volvo and Saab cooler cores an unfair advantage
in this test, as the transition from leaf blower tube to intercooler inlet
is much better, and produces less backpressure. No one I know runs 3" intercooler
tubing, so the advantage of 3" inlets vanishes in real life. To be totally
fair in comparing cores, I subtracted only an inch (water)
of backpressure from the Saab and Volvo coolers, while I subtracted
2" from the others. This really doesn't change much, but gives a better
comparative reading of the core's ability to flow air.
Voltage to the leaf blower was constant at 120V, ranging from 120.3V to
120.6V during the test.
Surprises? Yes!
The Ford cooler looked like it would flow much better than it did, but
it is JAMMED full of internal fins for better cooling, so that explains
why.
I doubted that the "big" volvo and Saab coolers would outflow the stockers,
and even doubted that they would MATCH the stockers, but they *did* just
about match them! The Volvo's extra tubes helped it whip the Saab cooler.
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